I have been able to solve even the very hard puzzles by simply identifying all possible candidates and then eliminating values that are not probable by identifying singles, doubles triples. Only occassionally do I get stumped and must use the x-wing technique. Are these other techniques useful for solving the puzzle faster? I usually spend around 30-45 minutes on a very hard puzzle and 20-25 minutes on the hard ones. I don't go looking for the other patterns unless I get stuck. I seek out the hardest and most evil 9x9 puzzles I can find. Just curious, that's all.

It sort of depends on whether you are referring to a puzzle that is 'very hard' or to a puzzle that has been rated 'very hard' by a particular person/program. Puzzle ratings differ widely in what each is called and in what techniques may be 'required' to solve them. Each puzzle setter has their own scale (very easy, easy, medium, hard, very hard vs. easy, hard, very hard, super hard, super-duper hard). Puzzle ratings can only tell you how hard a puzzle is in relationship to how hard other puzzles by the same setter are. It is my understanding that until very recently the puzzles listed as 'very hard' on this site could be solved with nothing more complex than triples. Lately x-wing has been added to the stew.

In some circles, the techniques required to solve a 'very hard' on this site are considered basic and no puzzle that limited itself to them would be considered 'hard' much less 'very hard'. Much of it depends on ones solving ability (knowledge of techniques and ability to use those techniques) and the puzzles to which one is exposed. If you limit yourself to puzzles on this site and ones in (most) newspapers, then you've learned all you need to know. But, if you do a bit of exploring, you'll undoubtedly find puzzles that you'll barely dent with those techniques, so "these other techniques" become necessary, not just to do them faster, but to do them at all.